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The most direct approaches for lignin depolymerization typically utilize thermal environments (e.g., pyrolysis) or liquefaction (including in water or organic solvents). If tuned appropriately, these processes can yield fuel oils or upgradeable vapors and oils from lignin. This chapter reviews the extensive thermal and solvolysis literature and comments on the applicability of these approaches for particular lignin conversion strategies, primarily into fuels or fuel oils.

info:eu-repo/semantics/published

Biomass densification elevates the bulk density of the biomass, providing assistance in biomass handling, transportation, and storage. However, the density and the chemical/physical properties of the lignocellulosic biomass are affected. This study examined the changes introduced by a briquetting process with the aim of subsequent processing for 2nd generation bioethanol production. The hydration properties of the unprocessed and briquetted wheat straw were characterized for water absorption via low field nuclear magnetic resonance and sorption balance measurements. The water was absorbed more rapidly and was more constrained in the briquetted straw compared to the unprocessed straw, potentially due to the smaller fiber size and less intracellular air of the briquetted straw. However, for the unprocessed and briquetted wheat straw there was no difference between the hygroscopic sorption isotherms, which showed that the amount of cell wall water was not affected by the briquetting process and that the sugar yield was similar after a combined hydrothermal pretreatment and enzymatic hydrolysis. The factors which offset the benefits introduced by the briquetting process need to be further examined to optimize the processing parameters and enzyme recipe for better use of the wheat straw biomass feedstock

To mitigate climate change it is necessary to further increase the deployment of renewable energy, including bioenergy. This analysis shows how this can be achieved in Danish agriculture and forestry before 2020. The key is a sustainable intensification and we show through three scenarios how it is possible to increase production while at the same time decreasing environmental impact and with only minor consequences on food and feed production. An additional ~10 Tg biomass can be available in 2020 for the Danish energy sector. By converting the biomass in a biorefinery concept it is possible to supply relevant, domestically produced energy carriers that amounts to ~ 5-13 % of 2020 Danish energy consumption. This has the potential to reduce the GHG emissions with 13-21 % of 2020 emissions. These results are possible because Danish net primary production and the human appropriation hereof can be increased. We show that biomass for bioenergy has a large near-term potential to supply relevant energy carriers to the society while at the same time achieving significant GHG emission mitigation.

Lignocellulosic biomass is a candidate for future renewable energy resources. Choice of optimum biomass types and biological conversion techniques requires well-founded assessment of the digestibility determining the conversion efficiency. The aim of this study was to investigate and evaluate the digestibility of miscanthus samples that were tested using three methods: 3,5-dinitrosalicylic acid assay (DNS), anaerobic batch digestion test, and high-throughput pretreatment and hydrolysis method, including a grinding and hydrothermal pretreatment prior to the analysis (HTPH). The miscanthus samples were expected to have different digestibilities due to maturity stage, dry matter content and the implementation of extrusion as a mechanical pretreatment. The results of the DNS and the biogas batch test methods were highly correlated (R2 between 0.75 and 0.92), but not with the results of the HTPH method. The DNS and biogas batch test showed that digestibility differed between samples, probably due to the degree of lignification and content of soluble sugars. For the HTPH method, the digestibility for biorefining was the same irrespective of the variation in the other analyses. The HTPH method had higher biomass use efficiency, closely followed by the biogas batch test running for 91 days on the mechanically pretreated biomass. The HTPH method provided information on the overall quantity of carbohydrates that can be made available from a given biomass. Additionally, DNS and biogas batch test visualize the variation in digestibility between biomass types caused by lignification and particle. The study concludes that the choice of evaluation method for miscanthus will depend on the bioenergy conversion method used and that important information on the interaction between physio-chemical pretreatment and biological accessibility of the biomass can be obtained by comparing the methods. This information will enable sound decisions on the future choice of bioenergy

Here we show how increased bioenergy production can be targeted through changes in management of rainfed, temperate agriculture and forestry. Bioenergy production can be substantially increased with reduced environmental impacts and minor effects on food and feed production. Even though global net primary production (NPP) may constitute a planetary boundary for bioenergy production, we show that at regional scale NPP can be increased and the human appropriation hereof (HANPP) may be sustainably increased. If this biomass is used for bioenergy in the form of highly relevant energy carriers, greenhouse gas emissions can be significantly reduced.

Wheat is one of the most important crops for food and feed and its straw is a potential feedstock for biorefinery purposes. Nitrogen (N) is an essential input factor in wheat agriculture but no information is available on how it affects straw composition during maturation and at harvest. To investigate this, we conducted a large scale field experiment in which wheat plants were cultivated at three levels of externally applied N. The plants were harvested at different stages of maturation, spanning green straw at heading (ear emergence) to fully yellow straw at final maturity. Defined parts of the straw were analyzed for cell wall characteristics relevant for further biomass processing. The straw N concentration corroborated with the level of N input, but the yield of straw biomass was not largely affected. High N treatment modified cell wall composition, namely increased abundance of arabinogalactan proteins (AGPs) and lignin in the mature straw. A general decrease in pectin methylesterification as well as in ferulate linkages was also observed. Importantly, no significant changes in crystalline cellulose and silicon concentration or in saccharification efficiency were observed among the different N treatments. Nitrogen fertilization partially alters the cell wall composition in wheat straw but is not a limiting factor in wheat biomass refinery.

The combination of NIR spectroscopy and chemometrics is a powerful correlation method for predicting the chemical constituents in biological matrices, such as the glucose and xylose content of straw. However, difficulties arise when it comes to predicting enzymatic glucose and xylose release potential, which is matrix dependent. Further complications are caused by xylose and glucose release potential being highly intercorrelated. This study emphasizes the importance of understanding the causal relationship between the model and the constituent of interest. It investigates the possibility of using near-infrared spectroscopy to evaluate the ethanol potential of wheat straw by analyzing more than 1000 samples from different wheat varieties and growth conditions. During the calibration model development, the prime emphasis was to investigate the correlation structure between the two major quality traits for saccharification of wheat straw: glucose and xylose release. The large sample set enabled a versatile and robust calibration model to be developed, showing that the prediction model for xylose release is based on a causal relationship with the NIR spectral data. In contrast, the prediction of glucose release was found to be highly dependent on the intercorrelation with xylose release. If this correlation is broken, the model performance breaks down. A simple method was devised for avoiding this breakdown and can be applied to any large dataset for investigating the causality or lack of causality of a prediction model.

Light-driven activation of lytic polysaccharide monooxygenases (LPMOs) has been attributed to the transfer of high redox potential electrons from excited photopigments to the enzyme. However, due to the formation of reactive oxygen species (ROS) in such a system, not only electrons from the pigments but also ROS could be part of the enzyme mechanism. This work investigates the role of ROS in the oxidation of phosphoric acid swollen cellulose (PASC) by a light-driven LPMO system. Our results clearly show that the addition of superoxide dismutase or catalase to remove ROS did not attenuate the capacity of the light-driven LPMO system to oxidize PASC, as measured by formation of oxidized oligosaccharides. We conclude that ROS are not part of the light-driven LPMO activation; hence, transfer of high redox potential electrons from the excited photopigment to the LPMO remains the most likely mechanism under the conditions tested in this study., info:eu-repo/semantics/published

Corn (Zea mays) cob is presented as a low-cost, abundant and sustainable material for the production of high quality activated carbons. In this study, a series of activated carbons were prepared by decomposition of the organic matter using a double-step process: pyrolysis followed by chemical activation with KOH, ZnCl2or H3PO4. The effect of pyrolysis temperature, different chemical agent and reaction time was studied and thus their importance for the properties of the activated carbons. The characterization of the activated carbons included elemental composition (CHNS), adsorption capacity (Iodine number and Methylene blue), surface chemistry (Fourier Transform Infrared Spectroscopy and Raman Spectroscopy) and textural characterization (Scanning Electron Microscope). Based on the results obtained, the decomposition of the corn cob was almost completed at 600°C. The activation presented diverse results depending on the activating agents used: while KOH showed good results, the chemical agents ZnCl2 and H3PO4 did not show a good performance of the activation process. The reaction time was also important in the activation process as better results were obtained after longer holding times. Among the different activated carbons, the one prepared by using pyrolysis at 600°C and activated with KOH for 2h showed the highest adsorption capacity. Its large surface area is suggested to enable the electron transfer and ion diffusion in the carbon matrix. However, parameters such as concentration of functional groups on activated carbon surface and pore-size distribution must be studied further in order to determine their importance for the activated carbons performance as capacitors.

There is a growing interest in lignin valorization to biofuels and chemicals. Here, we propose a novel and simple noncatalytic process to directly liquefy lignin rich solid residual from second generation bioethanol production by solvolysis with ethanol. Through an extensive parameter study in batch autoclaves assessing the effects of varying reaction temperature, reaction time, and solvent:lignin ratio, it is shown that hydrothermally pretreated enzymatic hydrolysis lignin solvolysis in supercritical ethanol can produce a heptane soluble bio-oil without the need for exhaustive deoxygenation. The process does not require addition of catalyst or a reducing agent such as hydrogen. The process is advantageously carried out with a low reaction period ((<1 h) and with a reduced amount of solvent to lignin feedstock (ethanol:lignin (w/w) ratio of 2:1) which is a previously unexplored domain for lignin solvolysis. The resulting bio-oil product is mainly a mixture of di- and monomeric lignin species where the original lignin unit linkages have been broken. The oxygen content is lowered to <10 wt %(corresponding to an HHV of 36 MJ/kg) and the bio-oil is stable and acid free (verified by NMR), and due to the use of sulfur free lignin rich residual as feedstock, the resulting oil product is equally sulfur free. The residual solid product (char) has a reduced oxygen content relative to the lignin feed and equally increased higher heating value, making it a candidate for use as a biochar.

When agricultural residues are processed to ethanol, lignin and silica are some of the main byproducts. Separation of these two products is difficult and the chemical interactions between lignin and silica are not well described. In the present study, the effect of lignin-silica complexing has been investigated by characterizing lignin and silica coprecipitates by FTIR and solid state NMR. Silica particles were coprecipitated with three different lignins, three lignin model compounds, and two silanes representing silica-in-lignin model compounds. Comparison of 29Si SP/MAS NMR spectra revealed differences in the distribution of silanol hydroxyl groups among different coprecipitates. These differences are dependent on the lignin type. The results are interpreted that the underlying mechanism of the interactions is the formation of hydrogen bonds between lignin aliphatic hydroxyl or carboxyl groups and the silanols, but not a condensation of the silica-in-lignin among the silica particles and not the formation of C-O-Si bonds.

Oxidative processes are essential for the degradation of plant biomass. A class of powerful and widely distributed oxidative enzymes, the lytic polysaccharide monooxygenases (LPMOs), oxidize the most recalcitrant polysaccharides and require extracellular electron donors. Here we investigated the effect of using excited photosynthetic pigments as electron donors. LPMOs combined with pigments and reducing agents were exposed to light, which resulted in a never before seen 100-fold increase in catalytic activity. In addition, LPMO substrate specificity was broadened to include both cellulose and hemicellulose. LPMO enzymes and pigment derivatives common in the environment of plant-degrading organisms thus form a highly reactive and stable light-driven system increasing the turnover rate and versatility of LPMOs. This light-driven system may find applications in biotechnology and chemical processing.

The report by Naudts et al. concludes that forest management in Europe during the last 260 years has failed to result in net CO2 removal from the atmosphere. The authors have reached this conclusion through their failure to consider a key factor in their otherwise comprehensive analysis. The authors present an analysis of net carbon emissions from forest, but omit substitution effects related to the link between forest management and the fossil carbon pool. The link between fossil and terrestrial carbon pools is however critical for modelling climate impacts. To conclude as they do, the authors should have asked: What would the GHG emissions have been in absence of forest management in Europe? The services provided by forest management - increased biofuel and materials production – substitute fossil fuels and materials, which are generally GHG-intensive. The report ignores that sustained yield forest management was developed to meet demands for energy and materials for an increasing population and prevented a complete destruction of Europe’s forest. Particularly since 1850, forest management has increased Europe’s forest area and productivity, and thus also the forest carbon pool as also reported by Naudts et al. By ignoring the link between forestry and fossil carbon pools and not considering development in the absence of forest management, there is no accounting for the effect on GHG emissions, and no basis for estimating the contribution of forest management to cl...

I denne afhandling undersøges en ny enzymatisk proces til blegning af cellulosepulp og fjernelse af hexenuronic acid (HexA). I processen indgår en haloperoxidase (Hap) og en tertiær amin (DABCO) der testes på oxygen-delignificeret eukalyptus kraft pulp. Ved at køre processen ved konstant pH (pH 4,5; 60°C) sås en øget lyshed samt en god respons på peroxid-alkalisk ekstraktion hvor mere end 80% HexA fjernelse opnået, uden at cellulose strukturen blev nedbrudt. I et optimeret, men ikke-bufret system, blev Hap/DABCO-systemet sammenlignet med en ikke-enzymatisk HOCl behandling, og en mindre effekt af Hap/DABCO-systemet blev fundet. På samme niveau af lyshed var HOCl behandlingen overlegen i forhold til reduktion af HexA og kappanummer. Hydrogenperoxid og ikke kun den enzymatiske oxidation kan være medvirkende til blegningen under Hap/DABCO behandling. Organochlor-dannelse blev målt og vurderet at være meget højere end reference-behandlinger med chloridoxid. Det blev konkluderet, at problemet med dannelse af organochlor skal løses før en fremtidig anvendelse af Hap/DABCO teknologien., A novel approach for cellulosic pulp bleaching and hexenuronic acid (HexA) removal using a haloperoxidase (Hap) and a tertiary amine catalyst (DABCO) was tested on oxygen-delignified eucalypt kraft pulp. In a buffered system (pH 4,5, 60°C), high brightness gain, good response to peroxide-reinforced alkaline extraction and more than 80% HexA removal were achieved, while preserving cellulose integrity. In an optimized, but non-buffered system, Hap/DABCO was compared to the non-enzymatic HOCl treatment and an inferior performance of the former was found. At the same brightness level, HOCl treatment performed superior in terms of HexA and kappa number reduction. Hydrogen peroxide was proposed as most likely playing a role in contributing to the brightening during Hap/DABCO treatment. Organochlorine formation was measured and found to be much higher than reference chlorine dioxide treatments. It was concluded that the problem of organochlorine formation must be solved for this technology to be used in the future.